  .a {
      position: relative;
      background: url(../../img/bg.jpg) no-repeat;

      width: 1600px;
      height: 600px;
      overflow: hidden;



      .b {
          background-size: cover;
          background: url(../../img/fm.jpg) no-repeat;
          width: 1600px;
          height: 600px;
          position: absolute;

          top: 0;
          left: 0;

      }
      .b:hover{
             transform: translate(100%);
          }
          
          
  }